It is the purpose of the proposed research to develop and test specific hypotheses regarding the central control of desynchronized sleep (D) at the level of single neurons by the method of chronic extracellular microelectrode recording. Results in hand indicate that the giant neurons of the cat pontine tegmentum (FTG), a region whose intrinsic anatomy and experimental destruction had suggested a role in D sleep, satisfy better than other cell groups three physiological criteria of a central control system: (1) greater selectivity of discharge during D sleep; (2) earlier anticipatory tonic rate change in transition to D sleep; (3) earlier anticipatory phasic rate change in association with the eye movements of D sleep. Long-term recordings show FTG neuronal activity to be (1) consistently selective across repeated D sleep cycles; (2) stereotyped, for each cell, within each cycle; (3) periodic when a series of cycles is considered. We have recently discovered that other cells, in the region of the locus coeruleus (LC), discharge in a tonically reciprocal fashion with respect to the FTG. All of these findings together suggest that FTG neurons function as output elements in an oscillatory brain stem system during D sleep. We have developed cell recording and data analysis techniques for simultaneous recording from FTG and LC neurons. On-line cross correlation will be performed to define reciprocal interaction and pairs of cells fulfilling these criteria will be recorded over several sleep cycles. The activity curves will be compared with predictions of a mathematical model.